1. Field of the Invention
The present invention relates to a control apparatus system, and more particularly, to an image forming apparatus and accessories therefor.
2. Description of the Related Art
As image forming apparatuses, there have been known LBPs (laser beam printers) and copying machines using electrophotography, and the copying machines each have sheet conveying devices, such as a paper deck, a finisher, and a stacker, connected thereto, as accessories. Conventionally, there has been proposed an image forming apparatus and accessories of this type (a control apparatus system, in a more broadly encompassing term), in which a main control section incorporating a CPU is provided so that the main control section can control the overall operation of the system in a centralized manner. In this case, the main control section directly drives units dispersedly disposed in the control apparatus system. For example, even when a motor drive unit is disposed at a location away from the main control section, the main control section generates a motor drive signal and transmits the drive signal to the motor drive unit through wiring, whereby a motor within the motor drive unit is driven by the drive signal.
Further, there has conventionally been proposed an image forming apparatus incorporating a plurality of CPUs (see e.g. Japanese Laid-Open Patent Publication (Kokai) No. H08-297436). More specifically, in the proposed image forming apparatus, the components of the image forming apparatus are classified into a plurality of units each forming a single control unit, on a function-by-function basis, and each of the units is provided with a CPU for controlling a controlled object in the unit. The units perform multiplex communication therebetween. The CPUs of the respective units each control a controlled object in the unit concerned while keeping consistency in control between the units. This configuration makes it possible to reduce the number of connecting wires other than connecting wires necessary for multiplex communication. Further, the configuration makes it possible to dispense with the provision of a main control section for controlling the overall operation of the image forming apparatus (the control apparatus system, in a more broadly encompassing term).
However, if the image forming apparatus disclosed in Japanese Laid-Open Patent Publication (Kokai) No. H08-297436 is to be redesigned, since controlled objects (loads) and control specifications are generally not the same as those in original designing or previous designing, it is difficult to develop a new apparatus by making use of the configuration of the old apparatus. For this reason, whenever the apparatus is to be redesigned, the development of an apparatus configuration optimum for the configuration of a device as a controlled object, and in particular, the development of an electric circuit board of the device needs to be carried out.
Even if the configuration of an old apparatus can be made use of, portions that can be utilized are generally limited to a limited few of a plurality of circuit blocks forming the electric circuit board of the apparatus.
Therefore, whenever an apparatus is designed or redesigned, costs and time for development are required, which results in an increase in the manufacturing costs of the apparatus and hinders reduction of time for development.